Theses and Dissertations from UMD
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Item DIRECTED AND ELLIPTIC FLOW MEASUREMENTS: A COMPARISON BETWEEN THE PARTICIPANT AND SPECTATOR PLANES IN Pb+Pb COLLISIONS AT √sNN = 5.02 TeV WITH CMS AT THE LHC(2024) Lascio, Samuel Andrew; Mignerey, Alice C.; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Directed and elliptic flow of unidentified charged hadrons at mid-rapidity are measured as a function of transverse momentum (pT) and pseudorapidity (η) in ultra-relativistic PbPb collisions at √sNN = 5.02 TeV with the Large Hadron Collider (LHC) at CERN. The reaction plane (RP) angle is approximated using participants and spectator neutrons measured with the Compact Muon Solenoid (CMS) detector and the newly installed Spectator Reaction Plane Detector (SRPD), respectively. The SRPD is the latest addition to the existing Zero Degree Calorimeter (ZDC) designed to measure spectator neutrons +/- 140 m from the interaction point at CMS. The Event Plane (EP) Method is used to calculate the v1odd, v1even, and v2 harmonic flow parameters as functions of η and pT. The directed flow measurements using participants and spectators with CMS are compared and contrasted. Overall results are in good agreement between participants and spectators, however v1even(pT) measurements using spectators begin to show the opposite trend to those using participants at pT > 2 GeV/c. Results are compared to those obtained by A Large Ion Collider Experiment (ALICE), which is another experiment at the CERN LHC. Directed flow results do not agree with those obtained by ALICE. Additionally, the first elliptic flow measurements using the EP Method and mixed harmonics with the SRPD are reported. A slight asymmetry in v2(η) is observed using spectators. The elliptic flow results do agree with ALICE. Tracking efficiency as determined by the CMS collaboration is applied to the data and potential corruption as a result is discussed. Results strongly support continued use of the SRPD as a spectator neutron detector for reaction plane determination within the CMS ZDC.Item DIRECTED FLOW MEASUREMENTS USING THE SPECTATOR PLANE WITH THE CMS DETECTOR IN THE 2018 PB-PB RUN AT √SNN = 5.02 TEV(2022) Adams, Eric Brian; Mignerey, Alice C; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Compact Muon Solenoid (CMS) is used along with the Spectator Reaction PlaneDetectors (SRPD) to measure the directed flow signal, using spectator neutrons, in the 2018 √sNN = 5.02 TeV Pb-Pb run with the Large Hadron Collider (LHC) at CERN. The Hadron Forward detector (HF), along with the tracker, is also used to measure the directed flow signal but instead uses participant nucleons. The results from the CMS 2018 Pb-Pb spectator and participant measurements of the directed flow signal are compared. These are the first spectator plane directed flow measurements from the CMS detector. The results are compared to the Pb-Pb collisions as reported by the A Large Ion Collider Experiment (ALICE) collaboration in 2013 [1].Item Directed Flow In Heavy Ion Collisions at sqrt{s_NN}=2.76 TeV(2015) Gomez, Jaime Arturo; Mignerey, Alice L; Chemical Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The directed flow of charged particles at midrapidity is measured in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV relative to the collision Event Plane, defined by the participant plane using various subdetectors. The rapidity-even directed flow component is measured for the first time using an Event Plane weighted by the transverse momentum of the emitted charged hadrons and found to be largely independent of pseudorapidity with a sign change at transverse momenta $p_{T}$ between 1.2 and $1.7$ GeV/c. These results are compared to measurements made by two other experiments at the LHC. Combined with the observation from ALICE of a vanishing rapidity-even $p_{T}$ shift along the spectator deflection plane is strong evidence for dipole like initial density fluctuations in the overlap zone of the nuclei. These observations open new possibilities for investigation of the initial conditions in heavy-ion collisions with spectator nucleons.